The present invention relates to a pivoting arm cut-off saw having a mechanism to retain the cutting arm assembly in a lowered position during storage and transport.
Pivoting arm cut-off saws are produced in a variety of different types and configurations. Pivoting arm cut-off saws intended to cut metal are frequently referred to as chop saws or abrasive cut-out saws, and are provided with a rotary abrasive wheel mounted on a pivoting arm for plunging into and out of a workpiece supported on a base. Typically, cut-off saws intended for metal use have a fixed pivot axis and a rotary fence enabling the workpiece to be positioned relative to the cutting plane to achieve a miter cut. Pivoting arm cut saws intended for woodworking come in a variety of configurations. Low price wood saws typically resemble abrasive cut-off saws for metal, except that a saw blade is substituted for the abrasive disc. The more expensive wood cut-off saws are provided with a miter adjustment enabling the pivot arm to be rotated about a vertical axis. Another configuration of a woodworking pivoting arm cut-off saw is referred to as a compound miter saw in which the pivot arm can be rotated to vary the miter angle, as well as being tilted about a horizontal axis to vary the tilt of the cutting blade, in order to achieve a compound miter cut. A sliding compound miter saw includes both miter and tilt adjustments, like a compound miter saw, while also having an elongate track enabling the saw blade and motor assembly to be moved horizontally when the blade is in the lowered position in order to cut relatively wide workpieces.
A common feature to all of the pivoting arm cut-off saws is that the cutting disc is mounted on an elongate cutting arm assembly, which is pivotably attached at one end to the base and is provided with a handle to allow the user to plunge the rotating cutting disc into the workpiece supported on the top surface of the base. A spring mechanism is typically provided to bias the pivoting arm assembly in the raised position.
When not in use it is desirable to lower the pivot arm so that the cutoff saw is more compact and easier to transport. A simple link chain and hook is a common way to hold the cutting arm assembly in the lowered position against the spring biasing force. The arm is simply moved to the lowered position and the chain is placed between the end of the arm and the base preventing the arm from rising. Although effective, this technique for maintaining the arm in the lower position is of poor aesthetic appearance and can be unreliable.
Various other techniques have been developed for maintaining the cutting arm in the lowered position during transport, such as a removable pin or a lock screw cooperating with a threaded bore. Particularly when used in metal cut-off saws, lock mechanisms, which require closely toleranced parts, such as screws and threaded bores are not effective because of the binding problems caused by metal cutting sand abrasive grit. Accordingly, it is the goal of the present invention to provide a simple low cost cutting arm assembly lock mechanism for maintaining the arm in the lowered position when the saw is not in use, which is strong, reliable and simple to operate, even when used in harsh abrasive environments.
The pivoting arm cut-off saw of the present invention is made up of three basic components, a base, a cutting arm assembly and a locking bar. The base has a top surface for supporting a workpiece and a through-slot defined in the top surface. The cutting arm assembly has a proximate end pivotally attached to the base and a distal end spaced therefrom terminating in a handle. The cutting assembly is disposed between the proximate and distal ends of the arm assembly and includes a motor and a rotatingly driven cutting disc. Pivotal movement of the cutting arm by the operator causes the rotating cutting disc to move toward the base and extend through the through slot in order to sever a workpiece supported on the top surface of the base. The locking bar temporarily locks the cutting arm in the lowered position when the cut-off saw is not in use. The locking bar is removable between a locked and unlocked position. The locking arm has a grip portion to be grasped by the user and a locking portion which, when the locking bar is moved to the locked position, is interposed between a pair of stop surfaces, one on the base and one on the cutting arm, to prevent the cutting arm from rotating to the raised position. When the locking bar is moved to the unlocked position the locking portion retracts sufficiently to enable the cutting arm assembly to rotate freely relative to the base.